Questions raised about reliability of carbon monoxide detectors

Dr. Andrei Kranz disconnected the carbon monoxide detector in his Long Island, N.Y., home last summer because the device kept going off for no apparent reason and waking the family.

In May, Kranz came home to find his parents, his 3-year-old daughter, the nanny and two houseguests dead in their beds, all victims of carbon monoxide poisoning.

Police investigators found that someone had turned on the air conditioner without shutting off the furnace. The air conditioner's intake filter was clogged with leaves, so the cooling system drew in furnace fumes instead.

Complaints about false CO alarms are common, and homeowners are tempted to disconnect the detectors. There is evidence, however, that "false" CO alarms may signal real, but hidden dangers.

Not everyone is convinced. False alarms became such an annoyance in Chicago that fire and utility officials pressed the U.S. Consumer Product Safety Commission in 1998 to force manufacturers to make new alarms less sensitive.

Doubts about the alarms' reliability caused Maryland lawmakers this year to reject, for a third time, legislation that would require CO detectors in new residences.

But some experts point to worrisome evidence of the detectors' effectiveness. Between 1993 and 1997, Minnegasco, a Minnesota utility, responded to as many as 4,000 home CO alarms a month. The utility's investigators found CO sources in 10 to 20 percent of the incidents.

The utility hired Steve Klossner to check again. Klossner, of Advanced Certified Thermography, took his detection gear to 50 houses where alarms kept going off but the utility had found nothing wrong. With extended monitoring, Klossner found CO sources in 49 of the 50 homes. Minnegasco technicians had missed them because the exposures were intermittent. Nine "were actually high enough to be lethal," he says.